Molecular detection of Toxoplasma gondii in wild oysters and seawater on the southeast coast of South Korea.

Toxoplasma gondii is the most common parasitic protozoan infecting approximately two billion people worldwide. Among various sources of infection with T. gondii, marine ecosystems, including marine bivalves, have been identified as a significant reservoir for the parasite. This study aimed to assess the potential risk of T. gondii through seafood consumption in South Korea. We surveyed the T. gondii GRA7 gene in wild oysters, farmed oysters, and seawater collected from the southeast coastal areas, monthly from April to August 2021. The gene was sequenced using the Sanger sequencing method, and 98.4 %-100 % identity to the T. gondii GRA7 gene was confirmed. Based on sequencing results, the overall prevalence of T. gondii was 1.3 % (4/300) in wild oysters and 6.6 % (3/45) in seawater, while all farmed oysters were negative throughout the survey. These findings suggest a low role of bivalves in T. gondii contamination in marine environments, highlighting the need for further investigation in South Korea. In addition, it is crucial to enhance inspection protocols for various food products contaminated with T. gondii and increase public awareness.